FIG. 10 shows a related art for improving air-mixing performance of cool air and warm air. According to the related art, three-layer streams of cool air and warm air are mixed. As shown in FIG. 10, cool-air passages J2, J3 are provided on both sides of a heating heat exchanger J1. Thus, warm air from the heating heat exchanger J1 is inserted between cool air from the cool-air passage J2 and cool air from the cool-air passage J3, which flow in parallel with the warm air, and the cool air and the warm air are mixed. Compared to the case where two-layer streams of cool air and warm air are mixed, a contact area between the warm air and the cool air is increased and air-mixing performance is improved.
According to JP-A-10-236134, which corresponds to U.S. Pat. No. 5,884,689, and US 2006/0027354, in order to control temperature differences of air blowing from multiple outlet portions, an air conditioner for a vehicle includes a bypass passage, which is arranged across an air mixing chamber, for directly guiding a part of warm air or cool air to the outlet portions of an air conditioning case.